Late to the party here, but as far as I can gather, if you choose to use variable offset, the end result is simply that you get at most 40 ADU extra headroom in the highlights.

I figure this on the published offset of 10 to be used at 0 gain. Now they're just saying 'keep it at 50' you could claw back another 40ADU, but this doesn't affect the noisy end of the image, only the highlights.

And let's face it, 40ADU isn't going to make much difference to an image.

I should also add, that my own experiments would imply that you can get away with much lower Offsets while still not clipping the read noise.

It's only really once you get into gains of 250+ that you need to be looking at using offsets over 30 ADU.

As I said in my first post (talking to myself here - sheesh!) I think that even if claw back even 40 ADU (best case) - I imagine that it will be only evident in the way the brightest stars are clipped.

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